Load controller

ABSTRACT

A system for regulating the output of a variable delivery hydraulic pump by sensing the load on the pumping members and adjusting the output of the pump in response thereto.

United States Patent 1191 Cattanach Apr. 10, 1973 [5 LOAD CONTROLLER 3,085,514 4 1963 75 Inventor: Hamish A. G. Cattanach, Middlesex, gggzg Z1322 Teddington, 3 29 067 [73] Assignee: Applied Power Industries, Inc., Mil- L453 11/1968 waukee Wis 2,298,850 lO/l942 2,715,875 8/1955 [22] Filed: Jan. 30, 1970 2,735,407 2/1956 3,085,514 411963 [21] Appl. No.: 7,206

FOREIGN PATENTS OR APPLICATIONS [52] US. Cl ..417/270, 417/281 4,080 9/1965 Great Britain ..417/2l4 [51] Int. Cl ..F04b 49/00 i 58 Field of Search ..417/13, 269, 271, Prlmwy EwmmerW1l11am Freeh 417/228, 281; 91/486, 489 Attorney-John Byrne [56] References Cited ABSTRACT UNITED STATES PATENTS A system for regulating the optput of a variable dehvery hydraullc pump by sensmg the load on the 2,937,801 5/1960 Berkoben ..4l7/28l pumping members and adjusting the output of the 2,999,463 9/1961 Cameron-Johnson ..4l7/202 ump in respgnse thereto, 3,056,358 10/1962 Pedersen et a1. ....91/489 3,066,609 12/1962 Hann ..91/489 4 Claims, 1 Drawing Figure LOAD CONTROLLER An object of this invention is to provide a control for a hydraulic pump for adjusting and limiting the pump flow to a predetermined value which may be fixed or adjustable.

A further objective of this invention is to provide a system for controlling the power of a hydraulic pump by sensing the force levels.

Another objective of this invention is to provide a system for controlling the power of a hydraulic pump adaptable to many pumping units of various design and function.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying diagrammatic-schematic drawing representing one embodiment of the invention.

Referring now to the drawing wherein like elements indicate like parts, numeral indicates the system of this invention. A pump 12 of a variable delivery type is used within the system. The output from pump 12 is delivered to a motor or load represented by the numeral 14. The pump 12 can be of the variable delivery type taught by my copending application 20,875, now US. Pat. No. 3,679,328, filed Mar. 27, 1970 which is a continuation of abandoned application US. Pat. No. 738,050 filed June 18, 1968, which in turn is a continuation-in-part application of abandoned application [1.8. Pat. No. 660,507 filed Aug. 14, 1967. In a pump of that construction, fluid output is variable to a sensing pressure communicated to the interior of the pump through a conduit 62. The conduit 62 as represented in the drawings of this invention corresponds to the conduit 62 of the above-mentioned copending application.

The pump 12 is of a type having a swash plate driven by a power shaft 22. Rotation of the swash plate reciprocates a plurality of circularly arranged pistons 24 in the manner well known to the art. The shaft 22 is keyed to the swash plate via the key 25. The piston thrust loads are taken by the bearing assembly 26 which is disposed between the swash plate and the end plate 28 of the pump. An annular plate 30 is disposed between the roller bearing members 32 of the bearing assembly and the interior surface 34 of the end plate 28. A recess 36 is formed in the surface 34 of the end plate 28. This recess (or recesses if desired) is communicated to a conduit 40 via a passageway means 42. The plate 30'covers the recess 36.

The drive shaft 22 is rotated by an external power source such as an electric or internal combustion engine. As the swash plate 20 is turned the pistons 24 are reciprocated through their intake and discharge strokes. The fluid source for the pistons is delivered to the pump assembly via the intake port 44. The intake chamber 45 is generally at reservoir pressures.

Disposed along the conduit 40 in that portion indicated as 40a, between the fluid source S and the passageway 42, is a fluid restrictor element 46. Disposed along conduit portion 40b is an adjustable valve member 52 which is communicated to tank via conduit portion 40c. As can be seen in the drawing, line 62 senses the pressure in conduit element 40c which extends between valve 52 and tank. An orifice 49 is disposed between point of junction of lines 62 and conduit element 400 and tank. The orifice 49 may be an independent element or, in some pump arrangement, the

existing leakage paths can be utilized for these purposes. As hereinafter described, the system will adjust the output of the pump to limit the load to a predetermined value which may be fixed or adjusted.

In operation, the source of fluid S is applied to conduit system 40. The leakage of fluid through passageway 42 and recesses 36 to tank pressures in intake chamber 45, is limited by the degree of restriction imposed by plate 28. The pressures the pistons exert against the swash plate 20 will be directly proportioned to the degree of restriction the plate 28 exerts. In other words, a hydrostatic pressure cell variable with thrust loads is provided which varies flow in the conduit system 40 in response to thrust force.

The valve 52 in conduit portion 40b is set open at a predetermined pressure which can be regulated or constant as required by the system involved. The valve 52 is a means for adjusting the torque input level on the pump inlet shaft; it being understood that the thrust forces of the pistons acting on the swash plate are converted to shaft torque. The valve 52 is set to open at predetermined levels to thereby bypass (via a control signal through passageway 62) the pumping chambers decreasing the piston thrust forces and the pump output. As fluid passes through the valve member, pressure will rise in conduit 62 which reduces the output of the pump in the manner known in the art. This will continue until the flow in conduit 40 is reduced.

Pressure in conduit portion 40c will fall as fluid escapes to tank through orifice 49. This causes the output of pump 12 to increase until a state of balance is achieved. As will be understood by those skilled in the art, the mechanism by which the delivery pump is made variable can be easily adapted for use with this system.

The system can be easily modified to vary the output of many know types of pumps. For instance, with a small modification to translate hydraulic pressures or flow to proportional mechanical movements, the system is adaptable for use with the US. Pat. Re. No. 25,298 issued to Stewart. In other words, the system is not limited to the particular variable control mechanism used by different pumping units. An essential part of the invention is that the load is sensed relative to the thrust forces absorbed by the pumps and these force levels are used to vary pump output.

In a general manner, while there has been disclosed an effective and efiicient embodiment of the invention, it should be well understood that the invention is not limited to such an embodiment as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principles of the invention herein described.

I claim: 1. A hydraulic pump system comprising a pump housing having one or more fluid inlet passages and one or more fluid output passages,

pumping members between said passages for delivering fluid to said output passages 'at greater pressures than exist at said inlet passages,

first means for varying the fluid output from said pumping members,

bearing means within said pump for carrying at least a portion of the forces developed by said pumping members,

a source of control fluid under pressure communicated to said bearing means, and

second means for generating an output signal through said control fluid in response to the level of said forces applied to said bearing means,

said first means being responsive to said output signal and said housing.

4. A hydraulic pumping system including a pump having a control means for adjusting the fluid output therefrom in response to hydraulic, signals, the im- 5 provement comprising:

bearing means within said pump, a source of fluid flow,

first means to vary said flow in response to thrust force levels in said bearing means, second means detecting the variations in fluid flow and adjusting said control means in accordance therewith. 

1. A hydraulic pump system comprising a pump housing having one or more fluid inlet passages and one or more fluid output passages, pumping members between said passages for delivering fluid to said output passages at greater pressures than exist at said inlet passages, first means for varying the fluid output from said pumping members, bearing means within said pump for carrying at least a portion of the forces developed by said pumping members, a source of control fluid under pressure communicated to said bearing means, and second means for generating an output signal through said control fluid in response to the level of said forces applied to said bearing means, said first means being responsive to said output signal to vary the Fluid output from said pumping members.
 2. The system of claim 1 wherein said control fluid is hydraulic fluid.
 3. The system of claim 1 wherein said pumping members are pistons riding on a swash plate assembly, said bearing means are located between said assembly and said housing and said output signal is generated responsive to the force level between said swash plate means and said housing.
 4. A hydraulic pumping system including a pump having a control means for adjusting the fluid output therefrom in response to hydraulic, signals, the improvement comprising: bearing means within said pump, a source of fluid flow, first means to vary said flow in response to thrust force levels in said bearing means, second means detecting the variations in fluid flow and adjusting said control means in accordance therewith. 